All of a sudden... running lean/misfiring? Input please :)

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FWD-3SGTE

New member
I'm gonna make this quick off the bat and I will update later (I'm at work right now)

So, without giving all of my specs and details, the car all of a sudden started to run real rough (sounds like its misfiring) and real lean (15.0+ AFR) after a 2nd gear pull. Motor is pretty fresh running on AEM with an AEM injector driver, 1000cc inj, Aeromotive pump, stock ignition, 35r turbo, MAP sensor (no MAF) yada yada yada.

In a dry rev, the motor sounds like a boxer motor, in gear, it runs rough like its misfiring all the time and lean as mentioned above. If I turn up the fuel press from 40psi to 50psi, it idles much better (high 11's to low 12's for a AFR) but still sounds like a boxer motor initially with a dry rev but still runs rough in gear but with better AFR (high 14's to low 15's)

I dont know if its misfiring because of the lean fuel mixture or because of bad spark....

To be continued... Boss is coming :p
 
G

gt4tified

New member
Its either one of two things....fuel or spark.

For fuel, do a fuel pressure test both before and after the fpr, check your injectors individually and check your fuel filter and the filter on the fuel pump also.

For ignition, check plugs, leads, rotor and dizzy, coil and igniter. Check ignition timing while you're at it to make sure it hasn't jumped.
 
F

FWD-3SGTE

New member
gt4tified":3hi8uaru said:
Its either one of two things....fuel or spark.

For fuel, do a fuel pressure test both before and after the fpr, check your injectors individually and check your fuel filter and the filter on the fuel pump also.

For ignition, check plugs, leads, rotor and dizzy, coil and igniter. Check ignition timing while you're at it to make sure it hasn't jumped.
Click to expand...

The crazy thing is that I have literally checked everything you have just mentioned except each injector individually (unsure of how to do this) and my igniter (it's a bitch getting the one off the alltrac to try out)

I've checked timing and that's good, tried plugs, wires, cap, rotor, dizzy and coil from the alltrac just to see if there was a difference and no. I've also changed the fuel filter and nothing there. I have plenty of voltage when in gear, and I simulated load by throwing the front of the car on jack stands and applying the brakes when in gear and my fuel pressure seemed to stay at my set point.

I'm kind of getting worried that it's a mechanical failure... our motors are non contact though correct? I mean I've checked for vacuum leaks, bad sensors (not many to check anyway) and no luck...

Ugh, problems like this lead to a lack of ambition :(
 
R

RedCelicaTRD

Moderator
I have not, but many others have. Same deal you are having, sudden lean condition. There is still a possibility is is not the injector driver, but taking it out of the loop at least eliminates a variable.
 
F

FWD-3SGTE

New member
RedCelicaTRD":h3b3zt0b said:
I have not, but many others have. Same deal you are having, sudden lean condition. There is still a possibility is is not the injector driver, but taking it out of the loop at least eliminates a variable.
Click to expand...

Alright, I'll see what I can do, mine as well try.
 
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WideFNopen

New member
I have almost the exact same symptoms on the rally car.

I just removed the harness ( again ) out of frustration since I all ready spent 50 hours testing everyting else and replacing all harness grounds.. Before the car would run about thirty minutes and then go lean and cut off. Now it stays lean right from start up to shut down.

If I can't find a problem with my harness im going to need to hire one of you guys to help get me going. I have the Black River Stage Rally in NY comng up at the end of Sept and I really cant afford another DNF. I gotta get ST1650002866 rollin asap.


Any help is greatly appreciated,

John
 
C

coyoteboy

New member
Definitely sounds injector related to me. If you have a seized/sticky injector it'll leak well enough to idle better when you up the fuel pressure etc.
 
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